Lubricating compositions



United s Edi LUBRICATING C(Hi EPGSITI QNS George Herbert Thornley, London, England, assignor to C. C. Wakefield & Co. Ltd., London, England, a British company NoDrawing- Application. January 21, 1954,

Serial No. 405,500

Claims priority, application Great Britain January 28, 1953 7 Claims. 01. 2s2 33.4

tent

of the lubricant film, coupled with its very low coefiicient of friction under conditions of boundary lubrication, give it a unique place among lubricants.

Castor oil and blends of castor oil with mineral lubri. cating oil have been extensively used for the lubrication of internal combustion engines, especially those operating under high loads and at high speeds.

Up to the present time such lubricants have suffered from the disadvantage that they have only been available within a very restricted range of viscosities. Mineral lubricating oils, on the other hand, as is well known, can be made avail-able over a very wide range of viscosities, and such oils have been used for lubricating internal combustion engines, having viscosities ranging from about 50 to about 400 seconds Redwood at 140 F., i. e., ranging from 5W to 50 according to the Society of Automotive Engineers (S. A. E.) classification.

The viscosity of castor oil has in the past been modified to a certain extent by blending with mineraloils of different viscosities, but it has not been found possible to bring about more than minor alterations. in viscosity by this means, owing to the limited solubility of mineral oil in castor oil (about maximum).

Another disadvantage associated with the use of lubricants consisting wholly or mainly of castor oil has been their tendency to form gummy deposits in the engine and on external parts such as exhaust pipes, etc., necessitating frequent changing of the oil and cleaning of the gummed parts. Improved lubricants having greatly reduced tendency to gum formation have been described in patent application No. 221,538, now Patent No. 2,692,858.

It will be appreciated that the viscosity of an oil which is to be used for lubricating an internal combustion enfi gine will depend on the design of the engine. Thus, certain engines designed to operate in conjunction with lubrieating oils of relatively low viscosity, e. g., in the S. A. E. 10W or category, will not run so efriciently on oils having viscosities in the S. A. B. 40/50 range, and therefore cannot be lubricated so effectively by castor oil or by conventional blends of castor and mineral oil such as have heretofore been employed. On the other hand, some of these engines, e. g. the engines of certain racing cars, cannot be lubricated so satisfactorily by mineral oils owing to the high piston speeds involved.

It is accordingly an object of the present invention to provide a lubricant, more especially a lubricant for internal combustion engines, which lubricant comprises a substantial proportion of castor oil, but which has a viscosity appreciably less than that of castor oil.

It is a further object of the present invention to provide a lubricant containing castor oil but which has a reduced tendency to gum formation.

According to the present invention, a lubricating composition comprises a mixture of castor oil and at least one relatively non-volatile substantially neutral organic ester, with or without the further addition of a, mineral lubricating oil.

The esters to be employed'should be relatively non-volatile, i. e., should have a boiling point of at least 200 C., and they should be readily miscible with castor oil at normal operating temperatures. In a preferred form of the invention the esters employed are the aliphatic or cycloaliphatic alcohol esters of organic dicarboxylic acids and may be represented by the general formula COORi where R is an alkyl, aryl, alkaryl or cycloalkyl radical, and R1 and R2 are the same or different, and are alkyl or cycl-oalkyl radicals.

In a preferred sub-class of these esters R=(CH2)n where n is a small integer from 2 to 8 and R1 and R2 are identical, and are branched-chain alkyl radicals having: at least 5 carbon atoms.

Specific examples of organic dicarboxylic acids from which the esters may be derived are: phthalic, succinic,

r maleic, malic, tartaric, pyrotartaric, glut-aric, adipic,

pimelic, suberic, azelaic, sebacic and picnic acids. It is preferred to use saturated acids.

The alcohols used in esterifying the dicarboxylic. acids should. be saturated aliphatic or cycloaliphatic alcohols such as methyl, ethyl, n-butyl and isobutyl alcohols, or, preferably, the higher branched-chain alcohols such as Z-ethyl n-heXyl, 3:5 :S-trimethyl-hexyl and capryl (1- methyl n-heptyl) alcohols, or a commercially available mixture of branched-chain C7 to C9 alcohols known as Alphanol 79. Alternatively, cycloaliphatic alcohols such as. methyl and dimethyl cyclohexanol may be used. If desired, there may be employed in place of ordinary alcohols, ethers or esters of polyhydric alcohols containing at least one free hydroxyl group e. g., ethylene glycol monobutyl ether or diethylene glycol monobutyl ether.

Although, as has already been stated, it is preferred to employ esters of dicarboxylic acids, other esters having a boiling point above about 200 C. may be used if desired. Thus it is possible to use simple esters such as 'amyl lactate or tricresyl phosphate, or the esters of polyhydric alcohols, especially dihydric alcohols, with monocarboxylic acids, especially those containing more than five carbon atoms. It is also within the scope of the present invention to use esters of polyalkylene glycols and glycol ethers such as the Ucon synthetic fluids. In selecting an ester it is preferred to avoid those containing unsaturated groupings, which are more prone to oxidation and decomposition, and those which are easily hydrolysed by Water yielding corrosive acids of low molecular weight.

Examples of specific esters which may be used in accordance with the present invention include:

Diet-hyl phthalate, di-n-butyl phthalate, di-isoamyl succinate, 'di-n-butyl ta-rtrate, di(2-ethyl hexyl) malate, triamyl citrate, di-(methyl cyclohexyl) adipate, di( Alphanol 79) aidipa te, di(2-ethyl hexyl) azelate, di(2-ethyl hexyl) sebacate, d-i(3:5 :5 trirnethyl hexyl) sebacate, dicapryl :sebacate, =di(Alphan ol 79) sebacate, dimet-hyl glycol phthalate, di(2-butoxye thyl) azelate, .triethylene glycol di- (2-ethyl hexanoate), amyl lactate, and tricresyl plros phate.

The relative proportions of castor oil and ester or esters which are to be employed will depend upon the desired viscosity of the final blend. Any blends may be employed within the range of 10% castor oil and ester to 90% castor oil and 10% ester.

In one form of the invention a proportion of mineral Viscosity Viscosity Example Blend at 140F., Index No. seconds 1 {90% Castor Oil 250 89 10% Dibutyl phthalate 50% Castor oil 25% D1 (3:525 trimethyl hexyl) seba- 2 cate. 120 108 25% Mineral oil oi viscosity about 70 seconds Redwood at 140F. 55% Castor Oil 10% Di (3:515 trimethyl hcxyl) seba- 3 cate. 120 80 35% Mineral oil of viscosity about 50 seconds Redwood at 140F. 49% Castor Oil 19% Di(2-ethyl hexyl) sebacate 4 19%tDi (3:525 trimethyl hexyl) seba- 103 113 ca e. 13% Mineral oil of viscosity about 70 seconds Redwood at 140F. 5 Castor oil 90% Dl(2-ethylhexy1) azelate 47 150 The lubricating compositions of the present invention, especially those containing a substantial proportion of the ester, will have less tendency to gum-formation in service than conventional blends of castor and mineral oil, and may therefore be employed without the addition of addirtives.

In a preferred form of the invention, however, the composition includes one or more additives to retard oxidation and gum formation. A preferred combination of additives is that disclosed in patent application No. 221,538, now Patent No. 2,692,858, in which an aromatic or heterocyclic secondary monoor poly-amine containing at least three cyclic nuclei at least two of which nuclei are aromatic nuclei attached directly to the nitrogen atom, is used in conjunction with an organic compound of tin .or antimony. Thus, for example, one may employ amines such as phenyl-wnaphthylamine, phenyl-fl-naphthylamine, fifi-dinaphthylamine, di-(B-naphthyl) -p-phenylene diam i-ne, phenothiazine, benzonaphthathiazine or Xylyl-fi-naphthylamine in conjunction with tin laurate, tin oleate, tin p-tertiary amyl phenol thioether, or preferably Ifill or antimony petroleum sulphonate.

Other additives which may be included with advantage are the triaryl phosphites and especially the phosphite esters of aromatic hydroxy-substituted thioethers and disulphides disclosed in Patent No. 2,396,839 which not only provide protection against corrosion of composite metal, e, g., copper lead bearings, but also serve to increase the load-carrying capacity of the composition.

Auxiliary additives which may be included in the composition are the reaction products of aldehydes or ketones with basic water-soluble primary or secondary amines, :as more fully described in our British patent specification No. 588,864. An example of such a compound is dimorpholinyl phenyl methane.

If desired, other additives, e. g., detergents and antioxidants operative at high temperatures, may also be present. Thus, for example, the composition may include detergents such as calcium petroleum sulphonate or basic barium petroleum sulphonate, or antioxidants such as oilsoluble metal salts of organic dithiophosphoric acids or metal derivatives of alkylated phenol thioethers or disulphides.

Specific examples of combinations of additives which 4 may be incorporated in any of the foregoing blends are:

1. 1.0% phenyl-fl-naphthylaimine 0.2% tin petroleum sulphonate i 2. 0.5% phenyl-,B-naphthylamine 0.2% tin petroleum sulphonate 1.0% di(3-carbometh'oxy-4-hydroxyphenyl) ithioether cresyl phosphite 0.2% di-morpholinyl phenyl methane 3. 0.25% zinc dim-methyl isoamyl) dithiophosphate 0.1% calcium petroleum sulphonate.

Further examples illustrative of the present invention are given in the following table which indicates how lubricants may be prepared, falling into various categories of the S. A. E.

Viscosity S. A. E. Example Blend at 140 F. Viscosity Classifi- No. (Redwood Index cation seconds) 15% Castor oil 42.5 D. O. 163 SW 10W In the foregoing table the following abbreviations have been used:

D. O. S.=di(2-ethyl hexyl) sebacate D. N. S.=di(3:5:5-trimethyl hexyl) sebacate D. O. A.=di(2-ethyl hexyl) adipate Oil A=mineral oil of viscosity about 50 seconds Redwood, at F.

Oil B=mineral oil of viscosity about 70 seconds Redwood, at 140 F.

In order to evaluate the performance of the lubricants of the present invention, the following engine tests were carried out:

A. Lauson engine test.-Tests were carried out in a standard H-2 type Lauson engine, under the following conditions:

Jacket temperature 210 F.i'2 F. Oil sump temperature 280 F.:2 F. Test duration 60 hrs.

Speed 1840 R. P. M.

The following test results illustrate the behaviour of a typical lubricant blend (blend A) of the present invention as compared with a blend of much higher viscosity, as hitherto employed (blend B).

Blend A consisted of:

49% firsts castor oil 13% mineral oil B (as previously specified) 19% di(2-ethyl hexyl) sebacate 19% di(3:5:5 trimethyl heXyl) sebacate 12.5% mineral oil of viscosity 44 seconds Redwood at. 140 F.

. p v 2% di(3-carbomethoxy 4-hydroxyphenyl) thioether cresyl phosphite 1% phenyl-fl-naphthylamine 0.2% tin petroleum sulphonate 0.2% dimorpholinyl phenyl methane This oil had a viscosity of 260" Redwood at 140 F., a viscosity index of 90, and fell within the S. A. E. 40

classification.

Piston Used oil Lacquer Bearing analysis, Lubricant Rating weight Percent (0. R. loss viscosity visual (mgs.) increase rating) B. Lauson Engine tests (high jacket temperature) Speed 2400 R. P. M. Load 4.0 B. H. P. Jacket temperature 350 F. Oil sump temperature 170/ 190 F. Fuel 2.5/3 ml. TEL/Gall. Time hours.

Oil con- Bearing sumpweight Piston Blend tion, (loss) rating Comments gm. er in s. 1...? g

Blend B 13.6 20 8. 2 1st and 2nd rings 50% stuck, soft gum on inlet underhead and exhaust valve stem. Blend A 9.2 29 8. 3 Top ring, lightly pinched, other rings free, soft gum on inlet underhead. Blend A... 38 7. 8 Top ring 55% stuck, (after 20 others free. No hours). change in inlet valve condition. Trace hard black deposit on exhaust valve neck.

C. Chevrolet engine tests.-Tests were carried out in a standard 216.5 cu. in. 6-cylinder Chevrolet engine under the following conditions:

D. Frictional horse-power (F. H. P.) and oil temperature characteristics.Tests were carried out in a 216.5 cu. in. 6-cy1inder Chevrolet engine, motored by an electric dynamometer under the following conditions:

Speed 3000 R. P. M. Induction depression 5" Hg. Jacket outlet temperature 200 F. (except where otherwise stated). The sump oil was allowed to reach a steady maximum temperature and F. H. P. recorded, at least three constant readings at 5 minute intervals being obtained. The sump w s h n rtific ally c oled to 220 RV and 20 an similar readings taken. For the final read ngsjacket temperature wasreduced to F., and maximum sump coolingemployed to obtain the lowest possiblesump temperature with each oil. Results, are tabulated below, a separate column showing, for interest, the viscosity of the oil at sumptempcrature.

It will readily be seen from the foregoing tests that blend A not only gave a performance equivalent to that of blend B in the normal Lauson and Chevrolet tests, but also effected a significant reduction in frictional horsepower. In the high temperature Lauson tests it also showed a marked improvement in ring sticking. In addition, blend A has been subjected to trials in a variety of highly-stressed motor cycle and motor car engines used in racing and record-breaking, and has given highly satisfactory results, the engines stripping in a very clean condition after test. For one new type of racing engine it was the only lubricant tried which gave a satisfactory performance.

I claim:

1. A lubricating composition consisting essentially of a mixture of castor oil, mineral oil and at least one ester selected from the group consisting of the aliphatic and cycle-aliphatic alcohol esters of organic dicarboxylic acids represented by the formula GOORi COORz where n is an integer from 2 to 8 inclusive and R1 and R2 are identical and are selected from the group consisting of branched-chain alkyl radicals and alkyl-substituted cycloalkyl radicals having at least 5 carbon atoms, the castor oil and organic ester each being present in the amount of at least 10% and the mineral oil being present in the mixture in an amount up to about 35% and in greater amount than would nomally be used in conjunction with the castor oil alone, the ester acting as a mutual solvent for the two oils.

2. A lubricating composition as claimed in claim 1 in which there is also incorporated a small amount of a compound selected from the group consisting of aromatic secondary mono-amines, aromatic secondary polyamines, heterocyclic secondary mono-amines and heterocyclic secondary polyamines containing at least three cyclic nuclei at least two of which nuclei are aromatic nuclei attached directly to the nitrogen atom in conjunction with an organic compound selected from the group consisting of tin and antimony organic compounds.

3. A lubricating composition as claimed in claim 1 in which there is also incorporated a small amount of a compound selected from the group consisting of a triaryl phosphite, a phosphite ester of an aromatic hydroxysubstituted thioether and a phosphite ester of an aromatic hydroxy-substituted disulphide.

4. A lubricating composition as claimed in claim 1 in which there is also incorporated a small amount of dimorpholinyl phenyl methane.

5. A lubricating composition as defined in claim 1 in which the ester constituent consists at least in part of di(3 :5 S-trimethyl hexyl) sebacate.

in which the ester constituent consists at least in part of di(2-ethy1hexy1) sebacate.

7. A lubricating composition as defined in claim 1 in which the ester constituent consists at least in part of 5 di(2-ethy1hexy1) adipate.

References Cited in the file of this patent 8 Morgan Ian. 25, 1944 Rogers Ian. 25, 1949 Beavers Mar. 7, 1950 Smith Dec. 19, 1950 Zisman Jan. 30, 1951 Vinograd et a1 Mar. 9, 1954 Evans et a1. Oct. 26, 1954 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OF CASTOR OIL, MINERAL OIL AND AT LEAST ONE ESTER SELECTED FROM THE GROUP CONSISTING OF THE ALIPHATIC AND CYCLO-ALIPHATIC ALCOHOL ESTERS OF ORGANIC DISCARBOXYLIC ACIDS REPRESENTED BY FORMULA 